Question

When I am databinding an entire page, I will do something like this:

Blah blah…

<%# SomeProperty == "GoodBye" ? "See you later" : "Hello" %>

And that works beatifully. However, often I will not use databinding for an entire page and write things the “clasic” ASP.NET way. E.g., in the code behind I will have something like:

lblSomeMessage.Text = SomeProperty == "GoodBye" ? "See you later" : "Hello";

And then .aspx would have

<asp:label runat="server" id="lblSomeMessage"/>

But what I want to do both…sort of. What I would like to do is not use databinding syntax but instead a code block:

<%= SomeProperty == "GoodBye" ? "See you later" : "Hello" %>
^^^^

Noe the output tag syntax. Now, the question is, when will this tag actually be evaluated? Suppose I don’t set the SomeProperty property until the OnPreRender event. Is that too late? In my testing I actually did this:

<%= SomeProperty == "GoodBye" ? + new System.Diagnostics.StackTrace().ToString() : "OH NO!" %>

And according to the stacktrace:

ASP.webform1_aspx.__Renderform1(HtmlTextWriter __w, Control
parameterContainer) at
System.Web.UI.Control.RenderChildrenInternal(HtmlTextWriter writer,
ICollection children) at
System.Web.UI.HtmlControls.HtmlForm.RenderChildren(HtmlTextWriter
writer)…

It happens during render, which is perfect. But is this guaranteed? Any gotchas to this rule?

Answer 1

Yes, it’s guaranteed to be Render.

“An embedded code block is server code that executes during the page’s render phase.” – http://msdn.microsoft.com/en-us/library/ms178135.aspx